1. Field of the Invention
The present invention relates to apparatus and methods for pressing powders, and more particularly to the making of ammunition and explosive charges.
2. Description of the Related Art
A variety of articles are prepared by pressing, or consolidating, powders either directly to form pellets, or into casings. In particular, the pressing of powders made from energetic materials to make explosive pellets or to fill projectile casings is associated with a number of problems.
A typical procedure for pressing energetic materials involves a large number of manual steps, many associated with safety issues of the pressing of energetic materials. The process requires manual weighing of powder, manual filling of a die or case, consolidating the powder, and manually performing off-line control testing.
When automatic filling is performed based on volume of powder, it is common for an improper amount of powder to be added to the die, resulting in a defective product that must be discarded after identification in a post-manufacturing inspection. With an energetic material, disposal of the defective product is a significant issue. Generally, determination of the quality of a produced item can only be determined by inspection after it is produced. In addition, record keeping for such a process is generally performed manually. This is tedious and involves substantial amounts of time after manufacture for correlating the manufactured items with the records.
In addition, improper filling of the die cavity of the press due to delivery of an improper amount of powder may additionally pose a safety issue. For example, too much of an energetic powder could conceivably increase the risk of explosion during the pressing step.
Moreover, the large number of manual steps associated with the process makes the process slow. In particular, it is necessary at several points in the process for the operators to leave the vicinity of the press to a safe room for fear of an explosion during a pressing step. This is tedious and adds considerably to the production time.
Examples of the contemporary art dealing with delivering controlled amounts of material are seen in the following U.S. Pat. No 4,843,579, to Andrews et al., entitled Weighing And Filling Method And Apparatus, describes a method and apparatus for dispensing measured amounts of powdered materials. The apparatus has a vibratory feeder, and deposits powdered material using a feeder trough into a container where it is electronically weighed.
U.S. Pat. No. 4,771,836, to Naito et al., entitled Control For A Weighing System, describes a system for combinational weighing.
U.S. Pat. No. 5,005,657, entitled Powder Dispensing and Measuring Device, describes an apparatus with a vibrating barrel for transferring powder, and a scale for weighing the discharged powder.
U.S. Pat. No. 5,114,630, entitled Continuous Manufacture And Casting, describes a system for manufacturing fluid products, particularly highly filled materials.
U.S. Pat. No. 5,387,095, entitled An Apparatus For Injection Molding High-Viscosity Materials, describes an apparatus for injection molding highly viscous materials. The apparatus is not designed for the handling of powders, however.
None of the above patents deals specifically with the issues of delivering weighed powder to a press.